//
// MemoryStream.h
//
// Library: Foundation
// Package: Streams
// Module:  MemoryStream
//
// Definition of MemoryStreamBuf, MemoryInputStream, MemoryOutputStream
//
// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_MemoryStream_INCLUDED
#define Foundation_MemoryStream_INCLUDED


#include <ios>
#include <iosfwd>
#include <istream>
#include <ostream>
#include <streambuf>
#include "Poco/Bugcheck.h"
#include "Poco/Foundation.h"
#include "Poco/StreamUtil.h"


namespace Poco
{


template <typename ch, typename tr>
class BasicMemoryStreamBuf : public std::basic_streambuf<ch, tr>
/// BasicMemoryStreamBuf is a simple implementation of a
/// stream buffer for reading and writing from a memory area.
///
/// This streambuf only supports unidirectional streams.
/// In other words, the BasicMemoryStreamBuf can be
/// used for the implementation of an istream or an
/// ostream, but not for an iostream.
{
protected:
    typedef std::basic_streambuf<ch, tr> Base;
    typedef std::basic_ios<ch, tr> IOS;
    typedef ch char_type;
    typedef tr char_traits;
    typedef typename Base::int_type int_type;
    typedef typename Base::pos_type pos_type;
    typedef typename Base::off_type off_type;

public:
    BasicMemoryStreamBuf(char_type * pBuffer, std::streamsize bufferSize) : _pBuffer(pBuffer), _bufferSize(bufferSize)
    {
        this->setg(_pBuffer, _pBuffer, _pBuffer + _bufferSize);
        this->setp(_pBuffer, _pBuffer + _bufferSize);
    }

    ~BasicMemoryStreamBuf() { }

    virtual int_type overflow(int_type /*c*/) { return char_traits::eof(); }

    virtual int_type underflow() { return char_traits::eof(); }

    virtual pos_type
    seekoff(off_type off, std::ios_base::seekdir way, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out)
    {
        const pos_type fail = off_type(-1);
        off_type newoff = off_type(-1);

        if ((which & std::ios_base::in) != 0)
        {
            if (this->gptr() == 0)
                return fail;

            if (way == std::ios_base::beg)
            {
                newoff = 0;
            }
            else if (way == std::ios_base::cur)
            {
                // cur is not valid if both in and out are specified (Condition 3)
                if ((which & std::ios_base::out) != 0)
                    return fail;
                newoff = this->gptr() - this->eback();
            }
            else if (way == std::ios_base::end)
            {
                newoff = this->egptr() - this->eback();
            }
            else
            {
                poco_bugcheck();
            }

            if ((newoff + off) < 0 || (this->egptr() - this->eback()) < (newoff + off))
                return fail;
            this->setg(this->eback(), this->eback() + newoff + off, this->egptr());
        }

        if ((which & std::ios_base::out) != 0)
        {
            if (this->pptr() == 0)
                return fail;

            if (way == std::ios_base::beg)
            {
                newoff = 0;
            }
            else if (way == std::ios_base::cur)
            {
                // cur is not valid if both in and out are specified (Condition 3)
                if ((which & std::ios_base::in) != 0)
                    return fail;
                newoff = this->pptr() - this->pbase();
            }
            else if (way == std::ios_base::end)
            {
                newoff = this->epptr() - this->pbase();
            }
            else
            {
                poco_bugcheck();
            }

            if (newoff + off < 0 || (this->epptr() - this->pbase()) < newoff + off)
                return fail;
            this->pbump((int)(newoff + off - (this->pptr() - this->pbase())));
        }

        return newoff;
    }

    virtual int sync() { return 0; }

    std::streamsize charsWritten() const { return static_cast<std::streamsize>(this->pptr() - this->pbase()); }

    void reset()
    /// Resets the buffer so that current read and write positions
    /// will be set to the beginning of the buffer.
    {
        this->setg(_pBuffer, _pBuffer, _pBuffer + _bufferSize);
        this->setp(_pBuffer, _pBuffer + _bufferSize);
    }

private:
    char_type * _pBuffer;
    std::streamsize _bufferSize;

    BasicMemoryStreamBuf();
    BasicMemoryStreamBuf(const BasicMemoryStreamBuf &);
    BasicMemoryStreamBuf & operator=(const BasicMemoryStreamBuf &);
};


//
// We provide an instantiation for char
//
typedef BasicMemoryStreamBuf<char, std::char_traits<char>> MemoryStreamBuf;


class Foundation_API MemoryIOS : public virtual std::ios
/// The base class for MemoryInputStream and MemoryOutputStream.
///
/// This class is needed to ensure the correct initialization
/// order of the stream buffer and base classes.
{
public:
    MemoryIOS(char * pBuffer, std::streamsize bufferSize);
    /// Creates the basic stream.

    ~MemoryIOS();
    /// Destroys the stream.

    MemoryStreamBuf * rdbuf();
    /// Returns a pointer to the underlying streambuf.

protected:
    MemoryStreamBuf _buf;
};


class Foundation_API MemoryInputStream : public MemoryIOS, public std::istream
/// An input stream for reading from a memory area.
{
public:
    MemoryInputStream(const char * pBuffer, std::streamsize bufferSize);
    /// Creates a MemoryInputStream for the given memory area,
    /// ready for reading.

    ~MemoryInputStream();
    /// Destroys the MemoryInputStream.
};


class Foundation_API MemoryOutputStream : public MemoryIOS, public std::ostream
/// An input stream for reading from a memory area.
{
public:
    MemoryOutputStream(char * pBuffer, std::streamsize bufferSize);
    /// Creates a MemoryOutputStream for the given memory area,
    /// ready for writing.

    ~MemoryOutputStream();
    /// Destroys the MemoryInputStream.

    std::streamsize charsWritten() const;
    /// Returns the number of chars written to the buffer.
};


//
// inlines
//
inline MemoryStreamBuf * MemoryIOS::rdbuf()
{
    return &_buf;
}


inline std::streamsize MemoryOutputStream::charsWritten() const
{
    return _buf.charsWritten();
}


} // namespace Poco


#endif // Foundation_MemoryStream_INCLUDED
